Ethanol and/or Isopropyl alcohol and/or n-propyl alcohol compositions with at least 60% percent v/v (approximately 52% by weight of alcohol) are well known to be antibacterial, therefore widely accepted for disinfecting purposes. Nonetheless due to the inherent characteristics of alcohol, it is perceived that the higher the content the better the product and a solution with higher than 60% by volume alcohol content is more desirable.
Alcohol disinfectant solutions are generally thickened in order to eliminate the waste and facilitate spreading the composition throughout the desired area. It is also known that other than gelling agents one can use paraffin or waxes to achieve thickening of a solution with high alcohol concentration. Such a composition with lanolin added to reduce the melting point closer to body temperature is described in U.S. Pat. No. 2,054,989. One of the disadvantages of gels and the above-mentioned type of thick alcohol-containing compositions is that if they do not leave a tacky feeling on the hands after one use (although some do), the effect builds up after repetitive use during the day, making it necessary to eventually wash off the thickeners before continuing the usage of an alcohol antiseptic solution. The present invention if formulated for the above-mentioned type of product does not leave such a feel, and does not need to be washed off after repeated use.
Generally speaking a high alcohol content disinfectant solution disinfects but does not clean. In order to make them disinfect and clean, so much soap would need to be added to the solution that the skin would feel soapy and disagreeable resulting in a formulation that would have little commercial appeal. Nonetheless, a non-irritant skin disinfecting formulation with a high content of a lower alcohol for use as a skin-washing agent has been successfully achieved by combining emulsifiers, surfactants and skin emollients as described in U.S. Pat. No. 5,629,006.
Surfactants other than for cleaning purposes are also used for spreading an aqueous composition containing one or more active substances rapidly and evenly over a surface due to their wetting properties. The use of good wetting agents definitely improves the efficient use of active substances in different compositions as described in U.S. Pat. No. 5,928,993.
Although a high alcohol content disinfectant solution has good disinfectant characteristics, it has a sharp smell and is generally perceived to cause drying of the skin, characteristics which can also be diminished to a desirable level in the present invention.
A foam product with greater than 40% v/v alcohol, which is easy and safe to use, is desirable over conventional liquid, gel or ointment type composition products. The concentration of alcohol already poses a hazard in itself, and there are many applications in which the perceived risk may be diminished if it could be dispensed as a foam. A foam intended to be useful as a skin disinfecting agent must have a uniform consistency, spreadability, cleansing ability, and have a pleasant feel, i.e. have rapid breaking power when pressure is applied; all of which present a challenge for a high lower alcohol content composition.
The description of an aqueous foaming skin disinfecting composition using 15% w/w alcohol as a co-solvent, which requires no pressurized container or added propellant to produce the foam, is described in U.S. Pat. No. 3,962,150.
The foam-forming agents utilized heretofore, have been incapable of forming stable foams when the liquid phase has high alcohol content without using other ingredients. Furthermore, lower alcohols have been considered to be defoamers rather than foam-promoting chemicals. According to Klausner, in U.S. Pat. No. 3,131,153, if more than 64% alcohol is used non-homogeneous compositions are obtained. The compositions in the patent required propellant to foam and the foams produced were of limited stability.
Various examples of compositions with a high content of a lower alcohol that are dispensed as a foam have been described, although for the purpose of the present invention the concentrations of alcohol and the levels of other ingredients are not suitable. More importantly, the use of propellants and aerosol containers to generate the foam is not desirable. For example, the compositions described in U.S. Pat. No. 5,906,808 disclose a product that uses an emulsifying wax NF, and a combination of stearyl and cetyl alcohol, or other wax combinations, which improve the foaming performance of the composition, in combination with cetyl lactate, to produce a 0.8% chlorhexidine gluconate alcohol product.
U.S. Pat. No. 5,167,950 issued to Lins discloses a foam product which requires a propellant and where no surfactant is added as a cleaning agent. The composition disclosed in this patent is based upon using an emulsifier system (fatty alcohol ROH 16-22 carbons) in combination with the use of a thickening agent (carbomer, klucel, etc.) to produce an antimicrobial aerosol mousse having a high alcohol content. The mousse includes alcohol, water, a polymeric gelling agent and a surfactant system comprising a C16-C22 alcohol, aerosol propellant and a non-ionic polyethoxylated surfactant.
U.S. Pat. No. 5,629,006 is directed to skin disinfecting compositions using alcohol, block copolymers which include polydimethyl siloxane-polyethylene oxide which contribute to antifoaming, and foaming surfactants such as ammonium lauryl sulfosuccinate. The formulations include thickening agents and the goal is to produce a disinfectant that foams like ordinary soap. The resulting product must be washed or rinsed off the user's skin.
Canadian Patent No. 2,534,692 is directed to a parasiticidal composition for head lice and requires a bio adhesive and is directed to head lice in which the bio adhesive is a high molecular weight carbomer related material which is used because they exhibit pediculicidal and ovicidal activity for killing lice and lice eggs respectively. Similarily to the previous referenced U.S. patent, the alcohol in this composition is only used as a carrier to deliver the carbomer/thickening agent which is the agent responsible for the killing activity sought by the inventors. As for the mixture with silicone, this is not present in all examples and when the silicone material and the alcohol are used the level of thickening agent would made it not possible for the composition to foam and the alcohol level is also below the desired disinfecting level that the present invention teaches.
Despite the work done to date it has been shown that there is little specific knowledge on how foams react and are formed, and surprisingly formulations that might seem not foamable result in the best foam producing ones while other formulations which seemed to have been producing foam even while being prepared did not perform well at all in some non-aerosol foam dispensers. The behaviour of aqueous foams is not the same as that of an alcohol foam.
Silicone-based surfactants have been used in applications requiring lowering of the surface tension and increased wetting properties, especially in applications that require materials to be compatible with solvent systems other than water and non-reactive to other components in the compositions. Silicone surfactants are desirable since they can achieve relatively low surface tension levels with relatively low concentrations in the compositions of interest. Commercial examples of the exploitation of the advantage of the low surface tension levels achieved using silicone based surfactants are crop protection products, printing inks, paints, floor coatings, etc. The characteristics mentioned above make silicone surfactants a candidate for the invention of this patent.
It would be very advantageous to have alcohol based disinfecting formulations containing silicone-based surfactants which may be dispensed as a foam under low pressure conditions and/or through an aerosol packaging system. Further, it would be very advantageous and desirable to find a foaming agent that could be used in concentrations that would allow it to be used in products that can remain in the area on which they have been applied and do not need to be rinsed or wiped off due to small amounts of residue remaining after evaporation. Thus it would also be very advantageous to provide foams that do not leave an unpleasant sticky after-feel as most commercial alcohol gel products are known to, or which clog up the dispensing equipment used to dispense the foams. Silicone-based surfactants are more than desirable for the purpose aforementioned since they are currently used as desirable cosmetic ingredients in creams, lotions, and other cosmetics due to their soft after-feel and properties.